This invention relates generally to electrical monitoring circuitry and more particularly, it relates to a wrist-strap monitoring system for monitoring continuously impedance of a human body via a wrist-strap connection worn on an operator's hand.
As is generally well-known in the electronic industry, there exists a wrist-strap which is a piece of wire worn by an operator so as to connect the operator to ground through a suitable resistance (i.e., one megaohm). In this manner, the build-up of electrostatic charge on the human body is prevented by attaching the human body to earth via the wrist-strap in order to drain off the charge before a problem occurs.
For example, an operator working in the manufacturing and assembling of semiconductor integrated circuits can develop an undesirable level of electrostatic charge in which the highly sensitive semiconductor integrated circuits may be damaged or destroyed when the potential is discharged. Therefore, it would be desirable to be able to monitor or detect that the wrist-strap is being worn by the operator so as to indicate a connection to ground. Further, it would be expedient to be able to detect when the ground connection is broken and to have a visual and/or audible indication of such condition. In addition, it would be further expedient to monitor continuously the impedance of a human body to be between an upper level and a lower level.